Giving permission to another user to edit my apps but error message shows...

[Chun_Cheung]

So I am trying to give permission to my fulfilment company to manage my stock and fulfilment but they keep getting this error on their side:

“To help protect your data, private app development is disabled

To make changes to your private apps or create new ones, ask the store owner to enable private app development.

Your existing private apps will continue to work.”

I look forward to your response.

How do I fix this???